Dual-Layer Lead Line for Secondary Battery Welding
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Solution Overview
Problem
Existing secondary battery welding techniques between electrode tabs and lead lines result in high internal resistance, limiting the efficiency of portable electronic devices.
Innovation Solution
A lead line with a dual-layer structure, where a high conductivity copper or copper-based alloy second layer is welded to the electrode tab, and a low conductivity nickel or nickel-based alloy first layer, covered by an insulating film to expose only the welding region, reducing internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer lead line is used for welding to electrode tabs, then the structure is simple and manufacturing is easy, but the internal resistance is high and welding characteristics are poor
Solution Approach 1:
The lead line employs a composite structure with a nickel-based alloy first layer and a copper-based alloy second layer. The nickel layer provides excellent welding characteristics with the electrode tab, while the copper layer provides high electrical conductivity to reduce internal resistance. This composite material approach resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The lead line structure is designed with different layers serving different local functions: the first nickel layer is optimized for welding contact with the electrode tab, while the second copper layer is optimized for electrical conduction. This local differentiation of material properties improves welding characteristics without compromising overall electrical performance.
2Reliability
If the entire lead line surface is exposed for welding, then welding access is improved, but electrical insulation is compromised
Solution Approach 1:
The lead line surface is segmented into a welding region where the insulating coating is removed to expose the nickel first layer, and a non-welding region where the insulating coating remains intact. This segmentation allows the welding process to access the conductive surface only where needed, while maintaining electrical insulation elsewhere.
Solution Approach 2:
The insulating coating acts as an intermediary layer that is selectively removed. It protects the lead line during manufacturing and handling, then is removed only in the welding region to allow electrical contact, mediating between the need for insulation and the need for welding access.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The dual-layer lead line structure enhances welding characteristics, reducing internal resistance and improving the performance of secondary batteries by optimizing the electrical connection between the electrode tabs and the protective circuit module.
Implementation Method 1
The second layer has a higher electrical conductivity than that of the first layer
Implementation Method 2
The lead line may be electric resistance welded to the electrode tab
Data Source
Figure 1~2
Figure 3A~3B
Figure 4
AI summary
A secondary battery including a bare cell. The bare cell includes an exposed electrode tab (124, 125) and a lead (300c, 300b) line welded to the electrode tab and configured to electrically connect the bare cell to a device electrically connected to the lead line. The lead line includes a welding region (320) and a lead region (330) excluding the welding region. The lead line is welded to the electrode tab in the welding region. The welding region includes a first layer (312) and a second layer (314). The second layer has a higher electrical conductivity than the first layer.